U.S. patent number 7,426,202 [Application Number 10/723,848] was granted by the patent office on 2008-09-16 for routing method for mobile wireless nodes having overlapping internet protocol home addresses.
This patent grant is currently assigned to UTStarcom, Inc.. Invention is credited to Chandra Warrier, Yingchun Xu.
United States Patent |
7,426,202 |
Warrier , et al. |
September 16, 2008 |
Routing method for mobile wireless nodes having overlapping
internet protocol home addresses
Abstract
In mobile IP wireless data networking, methods are described for
correctly routing packets through a foreign agent to or from
wireless nodes where the wireless nodes have the same home network
IP address. Instead of using normal IP routing, the foreign agent
uniquely identifies the wireless node's home network IP address and
home agent IP address with a PPP link address associated with a PPP
link between the foreign agent and the wireless node. This
association between PPP link addresses, home agent IP addresses,
and home network IP addresses, is preferably implemented in
software as a table stored in the foreign agent. The routing of
packets through the foreign agent to the mobile nodes is performed
by reference to the table. The table allows the foreign agent to
correctly and efficiently route packets in the situation where
multiple wireless nodes are registered with the foreign agent, but
more than one of the wireless nodes have the same home network IP
address.
Inventors: |
Warrier; Chandra (Schaumburg,
IL), Xu; Yingchun (Buffalo Grove, IL) |
Assignee: |
UTStarcom, Inc. (Alameda,
CA)
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Family
ID: |
30116158 |
Appl.
No.: |
10/723,848 |
Filed: |
November 26, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040136337 A1 |
Jul 15, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09491751 |
Jan 27, 2004 |
6684256 |
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Current U.S.
Class: |
370/338; 370/466;
370/469; 709/225; 709/226 |
Current CPC
Class: |
H04L
29/12311 (20130101); H04L 45/00 (20130101); H04L
45/54 (20130101); H04W 8/06 (20130101); H04L
61/2084 (20130101); H04W 80/04 (20130101); H04W
8/26 (20130101); H04W 40/36 (20130101) |
Current International
Class: |
H04J
3/22 (20060101) |
Field of
Search: |
;370/338 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
C Perkins, Request for Comments 2002 (Oct. 1996). cited by
other.
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Primary Examiner: Orgad; Edan
Assistant Examiner: Patel; Jay P
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation of U.S. patent application Ser. No.
09/491,751, filed on Jan. 27, 2000, now U.S. Pat. No. 6,684,256,
issued on Jan. 27, 2004. U.S. patent application Ser. No.
09/491,751 is herein incorporated by reference in its entirety.
Claims
We claim:
1. In a communication system for communicating with a plurality of
mobile nodes, the system having a plurality of home agents, the
plurality of home agents managing Internet Protocol (IP) addresses
in multiple address pools, the multiple pools having overlapping IP
addresses and each pool being associated with a unique home agent
IP address, a method comprising: in a foreign agent, receiving a
plurality of data packets from the plurality of home agents, each
packet containing an IP address of the respective home agent,
wherein at least one data packet destined for a given mobile node
has the same assigned home IP address as at least one other mobile
node; in the foreign agent, using a combination of the assigned
home IP address of the given mobile node and the IP address of a
home agent to identify a unique point-to-point protocol (PPP) link
for the given mobile node; and in the foreign agent, routing the at
least one data packet destined for the given mobile node to the
given mobile node using the unique PPP link.
2. The method of claim 1, further comprising: in the foreign agent,
receiving a packet from a mobile node over a PPP link, the link
associated with an associated PPP link address and the packet
containing a home IP address of the mobile node, using a
combination of the associated PPP link address and home IP address
to determine a unique home agent IP address, and routing the packet
to the home agent using the unique home agent IP address.
3. A communication system for communicating with a plurality of
mobile nodes in a communication system, the communication system
having a plurality of home agents, the plurality of home agents
managing multiple Internet Protocol (IP) address pools having
overlapping IP addresses, each pool being associated with a unique
home agent IP address, wherein a home IP address for a given mobile
node is associated with one of the multiple pools, the system
comprising: a foreign agent that uses a combination of the home IP
address and an IP address of a home agent from a packet to identify
a unique point-to-point protocol (PPP) link for the given mobile
node; and wherein the foreign agent routes the packet to the mobile
node using the unique PPP link, and wherein the foreign agent
receives a packet on a PPP link from a mobile node, the packet
containing a home IP address and a PPP link address associated with
the PPP link, and determines a unique home agent IP address from a
combination of the associated PPP link address and home IP address,
and routes the packet to the unique home agent IP address.
4. A foreign agent for use in a communication system for
communicating with a plurality of mobile nodes, wherein the
communication system comprises a plurality of home agents, the
plurality of home agents managing Internet Protocol (IP) addresses
included in multiple address pools, the multiple address pools
having one or more overlapping IP addresses and each pool being
associated with a unique home agent IP address, the foreign agent
comprising: a processing device; a storage device having a
plurality of machine executable instructions that, when executed by
the processing device, provide for: using a combination of an
assigned home IP address of the given mobile node and an IP address
of a home agent with which the mobile node is associated to
identify a unique point-to-point protocol (PPP) link for a given
mobile node of the plurality of mobile nodes; routing a packet
destined for the mobile node using the unique PPP link; receiving a
packet on a PPP link from a mobile node, the packet containing a
home IP address and the PPP link having an associated PPP link
address; determining a unique home agent IP address with the
associated PPP link address; and routing the packet to the home
agent using the unique home agent IP address.
5. A foreign agent for routing a data packet associated with a
given mobile node, the foreign agent comprising: machine executable
instructions that when executed provide for: processing the data
packet associated with the given mobile node, the processing
including: associating a home Internet Protocol (IP) address and a
home agent IP address contained in said data packet to determine a
unique point-to-point protocol (PPP) link address corresponding
with the given mobile node; routing the data packet to the given
mobile node via the unique PPP link address; maintaining a table
mapping PPP link addresses to unique pairs of home IP addresses and
home agent IP addresses, and wherein associating home Internet
Protocol (IP) addresses and home agent IP addresses is accomplished
by reference to the table, such that multiple mobile nodes having
the same home IP addresses but different home agent IP addresses
may be distinguished from each other.
Description
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates to the subject of mobile Internet Protocol
("IP") data networking.
B. Description of Related Art
Public packet switched networks can be used to carry traffic to and
from a mobile communications device, such as a laptop computer or
personal digital assistant equipped with a cellular telephone
modem. The basic architecture of mobile IP data networking is known
in the art and described in several publications, including the
Request for Comments document RFC 2002 (1996) and in the textbook
of Charles E. Perkins, Mobile IP Design Principles and Practices,
Addison-Wesley Wireless Communications Series (1998), the contents
of both of which are incorporated by reference herein.
Basically, in Mobile IP communication, a wireless mobile node
communicates with a terminal on an IP network by means of a foreign
agent and a home agent. Typically, foreign agent functionality is
incorporated into a network access server chassis located on a
mobile node's visited network. The foreign agent provides routing
services for the mobile node while it is registered with the
foreign agent. A Point-to-Point Protocol (PPP) session is
established between the mobile node and the foreign agent. The
foreign agent de-tunnels and delivers datagrams to the mobile node
that were tunneled by the mobile node's home agent.
The home agent is usually a router on a mobile node's home network
that tunnels datagrams for delivery to the mobile node via the
foreign agent when the mobile node is away from home. The home
agent maintains current location information for the mobile node,
through a variety of possible mechanisms, such as described in the
patent application of Richard J. Dynarski, et al., "Dynamic
Allocation of Wireless Mobile Nodes Over an Internet Protocol (IP)
Network", Ser. No. 09/233,381, which is incorporated by reference
herein. When multiple home agents are handling calls for multiple
mobile nodes simultaneously, the home agents are providing, in
essence, a service analogous to virtual private network services.
Each mobile node is typically associated with a separate home
network. The routing path from that home network, through the home
agent, to the foreign-agent and mobile node is like a virtual
private network for the mobile node.
The situation can arise in which two mobile nodes are
simultaneously registered with a foreign agent, and have
established a PPP session with the foreign agent, but the two
mobile nodes have the same home network IP address. In a typical
prior art foreign agent implementation, the overlapping IP
addresses will cause an IP routing failure, since more than one
routing table entry could have the same network address associated
with different PPP links. This overlapping IP address for both
mobile nodes could be a consequence of the home network assigning
the same IP address to the mobile node, either a priori or during
the mobile IP registration process.
Accordingly, there is a need in the art for a method for handling
overlapping IP address pools in a foreign agent. The present
invention solves that need and provides methods by which a foreign
agent can correctly route packets to a from any number of mobile
nodes that are simultaneously registered with the foreign agent but
have the same home network IP address.
SUMMARY OF THE INVENTION
In a first aspect, a method is provided for routing a data packet
through a foreign agent to a wireless node. The method is
specifically designed to handle the situation where multiple
wireless nodes are registered with the foreign agent but have the
same home network IP addresses. The method begins by receiving a
data packet at the foreign agent from a home agent associated with
wireless node. The foreign agent uniquely associates a home
Internet Protocol (IP) address and a home agent IP address
contained in the data packet with a Point-to-Point Protocol (PPP)
link address. The PPP link address is associated with a PPP link
previously established between the foreign agent and the wireless
node. This association is preferably implemented in software a
table. The foreign agent forwards the data packet through the
foreign agent to the PPP link (with the addressing done by
reference to the table) for transmission to the wireless node.
In a preferred implementation, the foreign agent maintains a table
mapping PPP link addresses to unique pairs of home IP addresses and
home agent IP addresses. The step of associating the incoming
packet from the home agent is performed automatically in the
foreign agent by reference to the table. Since, each wireless node
having the same home network IP address will have a different home
agent, multiple wireless nodes having the same home IP addresses
but different home agent IP address may be distinguished from each
other in the table and the foreign agent can correctly identify the
PPP link to forward the packet to the proper wireless node.
In the reverse direction, the foreign agent receives packets from
the wireless nodes, and some of the wireless nodes may have the
same home network IP addresses. However, the wireless nodes having
the same home network IP address will be associated with a separate
PPP link. Be reference to the table, the foreign agent can
determine which home agent to forward the packet to, since the home
agents are uniquely identified with a home agent IP address and a
PPP link address associated with the packet received from the
wireless node. The result is that in both directions, the foreign
agent can handle the situation where multiple wireless nodes are
active in the foreign agent but have the same home network IP
address. If conventional IP routing methods were performed, this
would not be possible.
These and other features and aspects of the invention will be
described in further detail in the following specification.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing the basic architecture for
providing mobile IP networking services for a plurality of wireless
nodes, two of which happen to have the same home network IP
address.
FIG. 2 is a illustration of a portion of the table that is
maintained in the foreign agent that is used to route packets to
the wireless nodes and to the home agents in accordance with a
principal aspect of the invention.
FIG. 3 is a flow diagram illustrating the method performed by the
foreign agent for forwarding of packets from mobile nodes to their
respective home agent.
FIG. 4 is a flow diagram illustrating the method implemented in the
foreign agent for forwarding of packets from the home agent to the
mobile nodes.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Overview of Representative Network System for Mobile IP Nodes
Referring now to FIG. 1, a basic architecture for providing IP
networking services for a group of mobile nodes is shown
schematically. In the example of FIG. 1, two wireless users,
designated 10A and 10B, exchange IP packets with host computers on
their home networks 11A and 11B, respectively. The wireless users
or nodes send and receive IP packets by means of a radio access
network 12 (the details of which are not important) and a PPP link
16 established with a remote access server 13 functioning as a
mobile IP foreign agent (also known in the art as an IWU/FA or
Interworking Unit/Foreign Agent). The foreign agent 13 has an IP
address (e.g., "C") which is used for tunneling data packets from
the home agents 20 to the foreign agent in accordance with the
mobile IP protocol.
The foreign agent 13 is on a network 14 maintained by a provider of
mobile IP service, such as a wireless communications company or
other suitable entity. The foreign agent 13 may be of the general
type of device described in the patent of Dale M. Walsh et al.,
U.S. Pat. No. 5,528,595 and assigned to the assignee of the present
invention. Such network access servers are available from companies
such as 3Com Corporation and Lucent Technologies. Basically, the
network access server/foreign agent implements foreign agent
functions as specified by RFC 2002 and provide access to an IP
local or wide area network 14 for the mobile nodes.
IP packets for the mobile devices are tunneled to the foreign agent
13 by a home agent in accordance with the Mobile IP protocol. In
the example of FIG. 1, a home agent 20A for mobile node 10A is
connected by one more intermediate networks 22 to the home network
11A for the mobile wireless node 10A. Similarly, the IP packets
from the home network 11B are transmitted over one or more
intermediate networks to the home agent 20B, where they are
tunneled to the foreign agent 13 for transmission to the mobile
wireless node 10B.
Each home agent 20 typically comprises a router with an interface
to the local area network 14 and a wide area network interface that
connects the home agent to intermediate networks 22 (which may be
an Asynchronous Transfer Mode network, frame relay network, or
other type of network). The backhaul network 22 is in turn
connected via suitable routers to the individual home networks 11A,
11B of the mobile nodes 10A, 10B respectively.
In the present example, mobile nodes 10A and 10B are assigned the
same home IP address, say "A". Both of them are connected to the
same foreign agent and have the same mobile IP foreign agent
care-of-address of "C" (IP address of foreign agent 13), for
tunneling purposes. Ideally, the foreign agent 13 tunnels traffic
from the mobile node 10A to the home agent 20A, which in turn
routes it via intermediate networks to the home network 11A for the
mobile node. Similarly, the foreign agent 13 tunnels traffic from
the mobile node 10B to the home agent 20B, which in turn routes it
via intermediate networks to the home network 11B for the mobile
node.
The problem with this situation is that, with both mobile nodes
having the same IP addresses on their home networks, if the foreign
agent 13 uses conventional IP routing schemes (as is the case for
remote access servers), it would not be able to properly route the
IP packets from the mobile nodes to the home agents. Similarly, in
the opposite direction the foreign agent 13 would not be able to
determine which mobile node 10A or 10B the packet is intended for
since the mobile nodes have the same home network IP address.
The present invention addresses this problem. Instead of using
conventional IP routing, a preferred embodiment of the invention
associates the address of the PPP link 16 between the mobile node
and the foreign agent to the IP tunneling information needed to
correctly route the packets to the proper home agent. In the
direction of home agent to mobile node, the foreign agent receives
a data packet associated with one of the wireless nodes from the
respective home agent. The foreign agent maintains a tunneling
table associating a home network IP address and a home agent IP
address contained in the data packet with a Point-to-Point Protocol
(PPP) link address in the foreign agent. The PPP link address
identifies the PPP link that is established between the foreign
agent and the wireless node. Since the home agent IP address and
home network IP address form a unique pair or set of information,
they can be used to uniquely, and correctly, identify the
associated PPP link for the packet and accordingly can be used to
tie any IP packets from the foreign agent to and from the mobile
node via the table. The foreign agent forwards the data packet to
the PPP link for transmission to the mobile node by reference to
the table.
FIG. 2 is an illustration of a representative tunneling table 50
maintained in software by the foreign agent and used to correctly
route packets to and from the mobile nodes when the overlapping IP
pool situation is presented. FIGS. 3 and 4 illustrate the method in
detail.
With reference to FIGS. 2-4, the process begins at step 70 when a
PPP link or session is established between the mobile node 10A or
10B and the foreign agent 13. During establishment of the session
and negotiation of protocols, such as IP Control Protocol (IPCP),
the foreign agent will allow the same IP address assignment for the
mobile node, that is, it will disregard the fact that another
mobile node is registered with the foreign agent with the same IP
address.
Once the PPP link negotiation is completed, the foreign agent will
perform mobile IP discovery procedures and wait for registration
request messages from the mobile node. When a registration request
message is received the foreign agent proceeds with registering
with mobile node, indicated in step 72.
Once registration of the mobile node is completed, the home network
IP address, home agent IP address and PPP link addresses are saved
in a tunneling table, as indicate at step 74, such as the table
illustrated in FIG. 2. The tunneling table can only be created
after a successful registration of the mobile node because a mobile
client could request dynamically a home IP address assignment at
the network layer.
In the table of FIG. 2, the numbers x.sub.1.x.sub.2.x.sub.3.2,
y.sub.1.y.sub.2.y.sub.3.4, z.sub.1.z.sub.2.z.sub.3.4,
g.sub.1.g.sub.2.g.sub.3.5 etc. are intended to simply represent
some particular IP addresses that are assigned to the PPP link in
the foreign agent, the home agent, and the mobile node on the home
network. The home agent IP address (e.g.,
p.sub.1.p.sub.2.p.sub.3.6) and home network IP address (e.g.
z.sub.1.z.sub.2.z.sub.3.4) form a unique pair of identifiers and
provide a unique PPP link address. Note that the first two entries
60 and 62 in the table 50 have the same home network IP address
(z.sub.1.z.sub.2.z.sub.3.4), but, since they have different home
agent IP addresses, they have different PPP link addresses. Thus,
the packets can be correctly routed to and from the mobile nodes by
maintaining a table such as illustrated in FIG. 2 and using the
table to either identify the proper PPP link for the home agent
(for traffic destined for the mobile node), or to identify the
proper home agent for the mobile node (for traffic received from
the mobile node and destined for the host computer on the home
network).
Thus, in the forward direction, and with reference to FIG. 4, an IP
packet is received by the foreign agent through the IP tunnel from
the home agent at step 76. The packet is decapsulated at step 78.
The PPP link to forward the packet to is identified at step 80 by
the outer source of the IP datagram (i.e., the home agent IP
address), and the inner destination address in the datagram (i.e.,
the home network IP address of the mobile node). The foreign agent
refers to the table of FIG. 2 to determine the PPP link to send the
packet to. There is no IP routing performed in this case. The
packet is forwarded at step 82 to the proper PPP link. The foreign
agent then waits for another packet from the home agent at step 84
and repeats steps 76, 78, 80 and 82 for subsequent packets. Of
course, this process is running in parallel in the foreign agent
for all the active ports and registered mobile nodes.
In the opposite direction, and with reference to FIG. 3, a packet
is received from the mobile node at step 90. The packets received
via each PPP link in the foreign agent is encapsulated at step 92
in accordance with the mobile IP protocol and tunneled to the
proper home agent at step 94. The tunneling table of FIG. 2 is used
to generate the tunneling information based on the unique set of
mobile node home network IP address and PPP link address to arrive
at the proper home agent IP address for tunneling the packet to the
home agent.
In accordance with this method, multiple wireless nodes having the
same home IP addresses but different home agent IP address may be
distinguished from each other in the tunneling table and proper
routing in both directions can be performed.
In the preferred embodiment, the foreign agent comprises a remote
access server having a plurality of ports (such as 24, 48, or even
200 or more in a high density embodiment). The remote access server
is provided with appropriate software and hardware for establishing
a PPP link with a wireless node at each port. Each port has its own
PPP link address. Further, the table shown in FIG. 2 is increased
to provide routing information for all the PPP link addresses
associated with the ports.
From the forgoing, it will be appreciated that we have described an
improvement to a foreign agent for a plurality of wireless nodes,
in which the improvement comprises providing a software program in
the foreign agent for handing routing of packets through the
foreign agent for the plurality of wireless nodes having a common
or overlapping home network address. The software program will
typically run on either a routing card or general purpose computing
platform incorporated into the foreign agent. Typically, the
routing card or computing platform provides an interface between
the foreign agent and a local or wide area IP network. The software
program comprising a set of instructions: (a) maintaining a table
(such as shown in FIG. 2) uniquely identifying links (that connect
the foreign agent to the plurality of wireless nodes) to home agent
addresses and home network addresses for the wireless nodes; and
(b) associating packets to be transmitted to the wireless nodes by
the uniquely identified links.
Accordingly, and as explained above, wireless nodes having the same
home network addresses but different home agent addresses may be
distinguished from each other in the table and proper routing of
packets through the foreign agent to or from the wireless nodes may
be achieved. Persons skilled in the art and familiar with mobile IP
data networking and foreign agents will be able to code such
software instructions from the present description without undue
difficulty. For example, the instructions may encode the procedure
shown in FIGS. 3 and 4. The procedures for establishing PPP links
with mobile nodes and registering of mobile nodes with a foreign
agent are known in the art and described in the mobile IP data
networking literature.
Persons skilled in the art will appreciate that various
modifications and alterations from the presently preferred
embodiment can be made without departure from the true scope and
spirit of the invention. This true scope and spirit is defined by
the appended claims, to be interpreted in light of the
foregoing.
* * * * *